Steve has been jumping up on my dresser and TV at night, and I got tired of sitting up in bed to hiss and act like I was actually coming over there in order to scare him down, so I finally got out a squirt gun after four or five jumps. I shook it before I used it, hoping to only have to use it once if he recognized the sound.
Sure enough, after one squirt, he totally recognizes the sound of a squirt gun being shaken. But for some reason, he finds it completely fascinating. He runs over to the bed and sniffs the gun, bites and paws at it, and digs some imaginary dirt next to it to try to hide it for later.
At least it gets him down from there. Stupid cat.